Question

Rewrite this sentence so that it begins with a prepositional phrase.
The members of the orchestra tuned their instruments.
Having found their seats, the members of the orchestra began to tune their instruments.
On the stage, the members of the orchestra began to tune their instruments.
Softly, the members of the orchestra tuned their instruments.
The instruments were tuned by the members of the orchestra.

Answer 1

A prepositional phrase is such a phrase which begins with a preposition (on, under, over, etc) and ends with a noun, pronoun, gerund, phrase etc.

So here, the correct sentence will be "On the stage the members of the orchestra began to tune their instruments".

Answer 2

The prepositions are the words which show the relationship between the pronoun and the nouns. On the other hand, the prepositional phrase starts with the prepositions and end with the object of a preposition, having one or more modifiers to describe.

Therefore, by rewriting the above sentence by using the prepositional phrases in a manner that encourages sentence variety within the sentence is,

On the stage, the members of the orchestra began to tune their instruments.